Scientists believe a labyrinth of disused mines underneath Glasgow could hold the key to heating the city's homes in the future.

Plans are being put in place to examine a vast reservoir of warm water that fills the mines and rock layers underneath the city in the hope of harnessing the natural heat store.

If the £9 million project proves successful, it could be rolled out in other towns and cities across Britain as the UK bids to become less reliant on fossil fuels.

Professor Michael Stephenson, director of science of the British Geological Survey (BGS), which is funding the project, said: "The rocks below Glasgow are crisscrossed with tunnels that were hewed into the rock by coalminers in the 19th and 20th century.

"Eastern Glasgow was once the location of some of Scotland's busiest mines. These old, long-abandoned tunnels should now be allowing water to flow freely beneath the city."

Scientists will initially drill narrow boreholes into the mines and use instruments to monitor temperature, seismic activity, water flow, acidity and other variables to establish the state of the water in the rocks below the city.

Because the reservoir is now linked by the tunnels, engineers believe they will not have to worry that the subterranean water will dry up at an individual location when they drill a borehole.

The aim of this first stage will be to establish whether this warm water can be extracted for long periods to heat Glaswegian homes.

Mr Stephenson said: "At present it is very hard to store energy and that is a problem when using renewable power plants - such as wind plants - which operate intermittently.

"Our second borehole array, again crammed with instruments, would allow us to test the feasibility of storing water - heated by renewable power plants - and then releasing that energy later when it is needed."

Researchers have long warned that the heating of homes is set to become a crucial issue.

While the UK is on target to decarbonise its electricity generation as a result of the growing numbers of renewable power plants, the nation is still heavily reliant on the North Sea and imported natural gas to heat its homes.

The use of these fossil fuels forms a substantial part of the carbon dioxide emissions which the UK has pledged to reduce.

"One solution would be to use the energy beneath our feet," Mr Stephenson added. "The temperature of the water that is sloshing through the old mines and in the rock layers under Glasgow is about 12C. That is not red hot, obviously.

"However, by using heat exchangers we can turn that mass of lukewarm water into a moderate supply of very hot water which could be pumped into homes to provide hot water and heating in winter. "

"At least that is the idea. Our underground observatory will determine whether it is feasible or not. It will analyse rates of replenishment, acidity, temperature and many other features.

"Based on that data we will know if we are on to a winner."

The Scottish BGS initiative - the Glasgow Geothermal Energy Research Field Site - will look at several sites throughout the city which have yet to be identified.

A second project has also been proposed for Cheshire, where scientists want to study rock conditions to assess the possibility of using underground vaults as storage for heated water.